Field
Embodiments of this invention relate to a fuel injection amount calculation method and a fuel injection controlling apparatus.
Description of Related Art
Conventionally, a controlling apparatus of an internal combustion engine for electronically controlling the fuel injection amount estimates an air amount to be taken into a cylinder, such air amount is hereinafter referred to simply as intake air amount, and calculates a fuel injection amount in response to the intake air amount. As a calculation method for the fuel injection amount, a method has been proposed in which, assuming that the control accuracy of the air fuel ratio is improved, an intake air amount is estimated from an intake pipe negative pressure and an engine speed of an internal combustion engine when the operation step of a piston is placed at the bottom dead center to determine a fuel injection amount. For example, refer to Patent Document 1 (Japanese Patent No. 3708574).
If time-dependent variation occurs with the tappet clearance of an internal combustion engine, then a displacement appears at opening and closing timings of an intake valve and an exhaust valve. Such displacement of the opening and closing timings of the intake valve and the exhaust valve sometimes makes the displacement of the intake pipe negative pressure in the proximity of the bottom dead center comparatively great although the variation of the actual intake air amount is small. Therefore, the conventional fuel injection amount calculation method described above has a problem that there is the possibility that the displacement between the actual intake air amount and the estimation value of the intake air amount may become comparatively great, resulting in failure in calculation of an optimum fuel injection amount.